Sure it can be a kernel misconfiguration problem, but NOT a kernel problem if its a recent one.
Things to also check:
->PPP : PPP echoes, PMTU discovery, bad MTU
->TCP : Bad rwin (default is OK and browser little page doesn't care), Window scaling (default is OK), Select ACKnowledgment (default is OK)
->Check the differences of this webpage in windows/linux : http://www.dslreports.com/stest/0
->Incorrect routing table (route -n)
->IRQ conflict (cat /proc/interrupts), wrong driver for your Ethernet card
->Bad network (this should be the case if windows is ok, but who knows. try ping -n <ipofgateway>, try ping -n <ipofgoogle>, try ping -n <ip of dns>)
->What constantly the logs (tail -f /var/log/message)
->Try to use wget on Linux and try also on windows, print the complete header + timing ( is the page cached only if using IE?)
->Launch tcpdump or ethereal. you will need some knowledge but this step can replace all others
I've always found linux network faster or same as windows.